package com.lagou.sqlSession;

import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

public class SimpleExecutor implements Executor {
    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... param) throws Exception {
        // 1. 注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();

        // 2. 获取sql语句 : select * from user where id = #{id} and username = #{username}
        //转换sql语句： select * from user where id = ? and username = ? ，转换的过程中，还需要对#{}里面的值进行解析存储
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        // 3.获取预处理对象：preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSql());

        // 4. 设置参数
        //获取到了参数的全路径
        String paramterType = mappedStatement.getParameterType();
        Class<?> paramtertypeClass = getClassType(paramterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();

            //反射
            Field declaredField = paramtertypeClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(param[0]);

            preparedStatement.setObject(i+1,o);

        }
        //5.执行sql语句
        ResultSet resultSet = preparedStatement.executeQuery( );
        //6.封装返回结果集
        String resultType = mappedStatement.getResultType();
        Class<?> resultClassType = getClassType(resultType);

        ArrayList<Object> objects = new ArrayList<>();
        while (resultSet.next()){
            Object o = resultClassType.newInstance();
            //元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            //metaData.getColumnCount() 数据库表多少个字段
            for (int i = 1; i <= metaData.getColumnCount(); i++) {
                //字段命
                String columnName = metaData.getColumnName(i);
                //字段值
                Object value = resultSet.getObject(columnName);

                //使用反射或者内省，根据数据库表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName,resultClassType);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o,value);
            }
            objects.add(o);
        }
        return (List<E>) objects;
    }

    @Override
    public int update(Configuration configuration, MappedStatement mappedStatement, Object... param) throws SQLException, Exception {
        // 1. 注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();

        // 2. 获取sql语句 : select * from user where id = #{id} and username = #{username}
        //转换sql语句： select * from user where id = ? and username = ? ，转换的过程中，还需要对#{}里面的值进行解析存储
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        // 3.获取预处理对象：preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSql());

        // 4. 设置参数
        //获取到了参数的全路径
        String paramterType = mappedStatement.getParameterType();
        Class<?> paramtertypeClass = getClassType(paramterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();

            //反射
            Field declaredField = paramtertypeClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(param[0]);

            preparedStatement.setObject(i+1,o);

        }
        //5.执行sql语句
        int resultSet = preparedStatement.executeUpdate();
        return resultSet;
    }

    private Class<?> getClassType(String parameterType) throws ClassNotFoundException {
        if (parameterType!=null){
            Class<?> aClass = Class.forName(parameterType);
            return aClass;
        }
        return null;
    }

    private BoundSql getBoundSql(String sql) {
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{","}",parameterMappingTokenHandler);
        String sqlStr = genericTokenParser.parse(sql);
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();
        BoundSql boundSql = new BoundSql();
        boundSql.setParameterMappingList(parameterMappings);
        boundSql.setSql(sqlStr);
        return boundSql;
    }
}
